Yeah, woeful speed for a second serve. Just look at it compared to Verdasco's, Kubot's and Janowicz's in those stats.
Now that is actually something I will be worried about on Friday. JJ is not the best returner on the first serve, but he can easily attack Andy's second serve.
Difference is, he often uses a lot of slice on his second serve - so naturally it's a good 20mph slower. The variety on it actually makes it far harder to judge, compared to two Poles who just tend to hit flat second serves. Harder, but easier to read.
Of course Murray does often tend to throw in particularly poor ones with little bounce or spin that get punished, but generally his second serve isn't as bad as the speed suggests. A lot more to serving than raw power.